The Brilliant Hack That Brought Foursquare Back From the Dead

The problem was the method the prototype was using to identify location €” a straightforward combination of GPS, Wi-Fi signals, and cell towers. It couldn’t always find the right signals, and even if it did, it tended to seriously drain the battery as it searched.

Why not take a shortcut? Foursquare already had a massive database of check-ins €” location information about the places its users most liked to go. And this data didn’t just include the place where someone had checked in. It showed how strong the GPS signal was at the time, how strong each surrounding Wi-Fi hotspot signal was, what local cell towers were nearby, and so on. Leveraging this data meant that Foursquare could still grab a good current location even if users were underground, near a source of radio interference, or facing some other signal obstacle. more> http://tinyurl.com/jvr4pnj